Perineurial-like Cells and EMA Expression in the Suprachoroidal Region of the Human Eye

The suprachoroidal region of the eye comprises vascular channels, melanocytes, and thin fibroblasts with elongated cytoplasm that are positioned directly adjacent to the densely collagenous sclera. Morphological similarities between these suprachoroidal fibroblasts and arachnoid cells and perineurial cells have been recognized, but whether these fibroblasts have a perineurial cell-like immunophenotype is not known. To further examine the relationship of these three cell types, we investigated the comparative expression of epithelial membrane antigen (EMA), the tight junction protein claudin-1, glucose transporter-1 (Glut-1), and CD34 in suprachoroidal fibroblasts, arachnoid of the optic nerve sheath, and perineurium of ciliary nerves in eight human eye specimens. Granular, diffuse, and cytoplasmic EMA expression was seen in suprachoroidal fibroblasts, but this was not contiguous with the similar pattern of EMA expression in adjacent perineurium and arachnoid. CD34 expression in suprachoroidal fibroblasts was also seen, similar to arachnoid and perineurium. Claudin-1 and Glut-1 were not consistently expressed in suprachoroidal fibroblasts, distinguishing them from perineurial cells in particular and suggesting that these fibroblasts do not arise directly from adjacent arachnoid or perineurium. Nonetheless, the overlapping morphology and protein expression suggest phenotypic similarities in these cells that protect and support adjacent retina, optic nerve, and peripheral nerve.